VENOUS SYSTEM 223 



Slit open one of the hepatic'sirmses, and follow it hack 

 into the corresponding lobe of the liver, noting its large size, 

 and the nv/merous veins opening into it. 



b. The Cuvierian simises are a pair of rather narrow 

 tubes, forming lateral continuations of the sinus 

 venosus, the hne of the pericardium marking the 

 boundary between the two. Each is about a 

 quarter of an inch long, and curves upwards from 

 the sinus venosus round the side of the oesophagus, 

 lying in a notch in the posterior border of the 

 fifth hypo-branchial cartilage. Each Cuvierian 

 sinus receives about the middle of its course the 

 inferior jugular sinus, and at its dorsal end the 

 great anterior and posterior cardinal sinuses, 

 i. The inferior jugular sinus, which is of small 

 size, can be traced forwards and inwards 

 along the outer wall of the pericardial cavity ; 

 and then forwards, ' close to the middle line, 

 and ventral to the gill-arches, 

 ii. The anterior cardinal sinus opens into the 

 Cuvierian sinus by a small aperture placed 

 immediately behind the fifth hypo-branchial 

 cartilage, and guarded by a very perfect valve, 

 the ventral flap of which is much the larger. 

 From the opening the sinus extends for- 

 wards as a very wide irregular space, situated 

 immediately above the giU-arches. In front 



Fig. 38. — Scyllium canicnla. DiBsection of the venous system Irom the 

 ventral surface. The right half of the lower jaw and the right 

 lobe of the liver have been removed, as has also the alimentary 

 canal behind the CBSophagus. (a. m. m.) 



Af nostril. AS, anterior cardinal sinus. H, right olfactory organ. 

 SV, saliclaTian rein. C, left half of lower jaw. D, fifth nerve crossing the 

 orbit. DC, ductus Cuvieri. E, right eye. F, out edge of floor of mouth. 

 Or, first branchial deft. H, ventricle. HS, left hepatic sinus. HV, left 

 hepatic vein. I, auricle. JV, left inferior jugular sinus. JV, opening 

 of right jugular sinus into sinus venosus. E, pericardial cavity. Ii, left lobe 

 of liver. XjV, right lateral vein. M, cesophagus, cut across. jJCV, hyoidean 

 sinus. IS, kidney or metanephros. O, communication between the right and 

 left posterior cardinal sinuses. OS, orbital sinus. P, post-orbital sinus. PS,pos- 

 terior cardinal sinus. PV, posterior cardinal vein. B.S, apertures of renal 

 veins into posterior cardinal veins. SA, aperture from sinus venosus to 

 auiiole. SV, sinus venosus. 



